In the construction and operation of certain optical systems such as, for example, laser beam optical transport systems, it is often required that the mirror systems employed in such systems be rapidly adjustable to permit active compensation for beam position jitter due to mechanical system vibration, ground motion, or laser system jitter.
Various provisions have been previously made for the adjustment of mirrors used in optical systems. Shull U.S. Pat. No. 3,953,113 teaches a laser mirror mounting device which provides for the exchangeability of sets of mirrors associated with various wavelengths of operation. The mirror mounting device is positioned within a housing which includes an adjustable internal reference surface for adjustment relative to an external reference surface included with the mirror mounting device. The device also includes support means for supporting a mirror relative to a laser and an adjustment means for adjusting the angular relationship of the mirror relative to the external reference surface.
Thompson U.S. Pat. No. 4,401,288 discloses an optical mirror mount in an upright position on a horizontal surface and which is adjustable in pitch and yaw. The mount includes a bracket having a horizontal leg and a vertical leg. Yaw adjustments are made by loosening mounting screws holding the bracket on a supporting surface and rotating the bracket about the mounting screw extending into the circular mounting hole in the horizontal leg. Pitch adjustments are made by turning an adjusting screw in a flexure spring until the vertical leg of the bracket is at the desired position in pitch.
Horton U.S. Pat. No. 4,293,112 describes apparatus for mounting and aligning an optical element on a support structure which comprises pivot means for mounting the element so that it can rotate about axes in two orthogonal directions and a pair of alignment means, each comprising a plunger and inclined guide groove. Adjustment means such as threaded screws, are provided for urging the plunger along the inclined grooves.
Reeder et al. U.S. Pat. No. 4,442,524 discloses a four-bar alignment adjustment mechanism with elastic hinges to enable the mirrors of a gas laser to be very finely tuned.
Koseki U.S. Pat. No. 4,672,626 describes the adjustment of the rear or output mirror of a laser oscillator by pivoting a laser mirror holder about three pivot points connecting the laser mirror holder and a support bracket. The first and third pivot points form an X-axis about which the holder may be rotated and the second and third pivot points form a Y-axis about which the holder may be rotated. The first and second pivot points are mounted so as to displace the holder in a direction parallel to the central longitudinal axis of the holder. Two control motors are disposed with their actuating shafts transverse to the central longitudinal of the laser mirror holder, at opposite sides of the holder and act against the first and second pivot points to adjust the angular alignment of the laser mirrors.
Koop U.S. Pat. No. 4,796,275 discloses a floating mirror mount in which a resiliently biased spring plate biases the mirror against a peripheral flange of a keeper while permitting the mirror to be lifted off the flange of the keeper when the front surface of the mirror is engaged by mirror positioning structure of a laser in the course of installing the mirror mount in a laser.
Great Britain Patent 2,059,143 describes a deformable support structure for supporting a controllable mirror for a laser. The support structure comprises a rim and a center post joined together by two spaced apart flexible membranes. Piezo-electric ceramic wafers are coupled to the support to provide adjustment of the mirror.
Russian Patent Abstract SU-901-968 describes the use of moving and stationary radially displaced discs interconnected by a screw thread in a gas laser optical system adjustment mechanism.
Tarabocchia et al., in an article entitled "Intracavity Tip and Tilt Adaptive Control Experiments" published in the Proceedings of the Society of Photo-Optical Instrumentation Engineers, Vol. 141 (1978), pp. 20-25, describe the use of a 2-axis tip and tilt dynamic mirror mount developed at Stanford Research Institute.
However, there remains a need for an adjustable mirror system capable of rapid adjustment with very little force so that an increased frequency of mirror compensation can be applied for beam jitter. There also remains a need for an adjustable mirror system wherein adjustment in either the X or Y axes may be made with a minimum of crosstalk between the axes.